The present invention relates to a single-tube color imaging apparatus having a striped color filter and more particularly to an apparatus which eliminates the problem associated with variation of beam scanning speed resulting from electrostatic potential differences between dark and bright areas on a photoelectrical conversion target.
In a single-tube color imaging apparatus, an optical image is focused through a striped color filter onto a photoelectrical conversion target to develop an electrostatic image which is scanned line-by-line by an electron beam. The color filter comprises successively arranged recurrent groups of color stripes of different colors. As the beam is scanned across the target, a color-multiplexed video signal is generated. This video signal comprises a "carrier" having a frequency inversely proportional to the interval at which the recurrent groups of the filter are arranged, the carrier being modulated in phase with the individual stripes of each recurrent group and in amplitude with the intensity of elemental areas of the incident image so that it varies in frequency inversely proportional to the intervals at which the recurrent groups of the strips are arranged and in phase with the relative values of primary color components contained in the color image passing through the stripes of each group and contains a phase deviation representing spatial differences between the strips of each group and a phase deviation representing nonlinearity in the speed of said electron beam in the direction of the line-by-line scan. The video signal is applied to a pair of synchronous detectors to which are also applied phase-shifted reference carriers. These reference carriers are derived from the pickup tube as it is illuminated uniformly with light of a predetermined color and stored into a memory prior to operation of the imaging apparatus. If the actual image is wholly or partially dark, the color-multiplexed signal will lose the carrier component, resulting in a loss of synchronism in frequency and phase with the phase-shifted reference carriers.